High resolution, low temperature electronic spectroscopy of mixed crystals of linear conjugated polyenes in inert host matrices is used to establish the electronic structure of these relatives of the visual polyenes. Major current interest centers on establishment of the nature of the lowest excited singlet state of simple alkyl substituted polyenes and the polyene aldehydes, CH3 (CH equals CH)n CHO. Very highly resolved spectra of two dimethylpolyenes have been obtained which demonstrate that the lowest excited singlet state of these compounds has Ag symmetry. BIBLIOGRAPHIC REFERENCES: "Conjugated Polyene Fatty Acids as Fluorescent Membrane Probes: Model System Studies," L.A. Sklar, B.S. Hudson and R.D. Simoni, J. Supramolecular Structure 4, 449 (1976). "Conjugated Polyene Fatty Acids as Fluorescent Probes: Spectroscopic Characterization," L.A. Sklar, B. Hudson, M. Petersen and J. Diamond, Biochemistry, in press (March, 1977).